81640015 has 8 divisors (see below), whose sum is σ = 100246608. Its totient is φ = 63792960.

The previous prime is 81640007. The next prime is 81640049. The reversal of 81640015 is 51004618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81640015 - 2³ = 81640007 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 189646 + ... + 190075.

It is an arithmetic number, because the mean of its divisors is an integer number (12530826).

Almost surely, 2^81640015 is an apocalyptic number.

81640015 is a deficient number, since it is larger than the sum of its proper divisors (18606593).

81640015 is a wasteful number, since it uses less digits than its factorization.

81640015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 379769.

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 81640015 is about 9035.4864285217. The cubic root of 81640015 is about 433.8114646846.

The spelling of 81640015 in words is "eighty-one million, six hundred forty thousand, fifteen".